Human Mixed Somatotrophic and Lactotrophic Pituitary Adenomas

Abstract

Six patients with acromegaly at examination were found to have pituitary adenomas composed of cells that secreted GH and PRL. This was demonstrated by the elevated serum hormone concentrations, by immunoperoxidase staining of 5 specimens, and by electron microscopic examination of 4. Ultrastructural characteristics, described in detail, suggest that these adenomas were mixed adenomas consisting of 2 well-defined, distinct cell types, each secreting one hormone. By immunoperoxidase staining some cells were found to contain immunoreactive growth hormone, other cells immunoreactive prolactin. No cells were detected exhibiting immunostaining for both growth hormone and prolactin. Eelctron microscopy, consistent with the results of immunostaining, revealed the presence of two distinct cell types, distinguishable from each other by their characteristic fine structural features. No intermediate forms were noted. Thus there was no evidence to suggest that one cell type might transform to the other. Present findings seem to indicate that mixed adenomas secreting growth hormone as well as prolactin and consisting of somatotrophs as well as lactotrophs do occur in the human pituitary gland. Although all the results obtained so far suggest that these tumors are composed of two distinct cell types and thus can be interpreted as representing real mixed adenomas, further work is required to establish whether or not they derive from one common progenitor.

Multihormonal Pituitary Adenomas

“…The present study confirms and extends previous reports (3,6,34) in that a large proportion of pituitary tumors have been shown to contain more titan one hormone. However, tumors associated with Cushings's disease contained only ACTH cells and not all tumors contained 0-LPH.…”

“…It is, therefore, important to analyze their cellular composition and the pattern of their hormonal secretion. Extensive electron microscopic studies revealed that the complexity of pituitary tissue is reflected by its tumors (3,29,31,32,41). The general conclusion of these studies was that the classic subdivision into inactive 'chromophobe' tumors, growth hormone (HGH)-secreting acidophil and corticotropin (ACTH)-secreting basophil adenomas is inadequate, because the secretory potentialities of the tumors are far more extensive than is implied in this classification.…”

Immunohistochemical Examination of Pituitary Adenomas

“…In several of the adenomas, hormones other than those increased in the serum were also detected, as reported elsewhere [3,7,10,27], However, this was the case in only a few cells and might explain why these hormones were not found to be elevated in serum above the upper limit of the normal range. It must also be considered that these cells cannot release their hormonal content, at least not in such a way that it reaches the circulating blood.…”

Growth hormone-secreting adenomas: pathology and cell biology

“…28 Three morphological tumor types that cosecrete GH and PRL can be identified as follows: the mixed GH cell/PRL cell adenoma, the mammosomatotroph cell adenoma, and the acidophilic stem cell adenoma. 12,24,26,28,31 Mixed GH cell/PRL cell adenomas and mammosomatotroph cell adenomas present clinically with acromegaly and mild hyperprolactinemia; on the other hand, patients with acidophilic stem cell adenoma present with hyperprolactinemia and only rarely with acromegaly. In our experience, these mixed tumors behave more aggressively than any pure GH-secreting adenomas with a lower surgical cure rate.…”